<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* 类选择器 */
    .textcolor {
      color: blue;
    }

    /* 后代选择器 */
    div span {
      color: red;
    }
  </style>


</head>

<body>
  <button class="textcolor">按钮</button>
  <p>段落1</p>
  <p class="textcolor">段落2</p>
  <div>
    <button>
      111
    </button>
    <span>span标签</span>

  </div>

</body>

</html>